制备奥托金的几种可供选择的方法

本文叙述三种由乌洛托品制备奥托金(HMX)的新方法,每种方法都是先进行乙酰化然后再硝化,其中以DADN为中间产物的方法的HMX得率,比目前以乌洛托品和醋酐为基础的Bachmann法要高,但要采用后者不必采用的硫酸和聚磷酸。已经表明,DADN可在中间规模以良好的得率快速连续地生产,废酸回收也没有什么问题。     

New inhibitors of the Tat-TAR RNA interaction found with a "fuzzy" pharmacophore model

TAR RNA is a potential target for AIDS therapy. Ligand-based virtual screening was performed to retrieve novel scaffolds for RNA-binding molecules capable of inhibiting the Tat-TAR interaction, which is essential for HIV replication. We used a "fuzzy" pharmacophore approach (SQUID) and an alignment-free pharmacophore method (CATS3D) to carry out virtual screening of a vendor database of small molecules and to perform "scaffold-hopping". A small subset of 19 candidate molecules were experimentally tested for TAR RNA binding in a fluorescence resonance energy transfer (FRET) assay. Both methods retrieved molecules that exhibited activities comparable to those of the reference molecules acetylpromazine and chlorpromazine, with the best molecule showing ten times better binding behavior (IC50 = 46 microM). The hits had molecular scaffolds different from those of the reference molecules.     

7-(Dialkylamino)coumarin-4-yl]methyl-Caged Compounds as Ultrafast and Effective Long-Wavelength Phototriggers of 8-Bromo-Substituted Cyclic Nucleotides

[7-(Dimethylamino)coumarin-4-yl]methyl (DMACM) and [7-(diethylamino)coumarin-4-yl]methyl (DEACM) esters of 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) and 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) are described as novel caged compounds for 8-bromo-substituted cyclic nucleotides. Synthesis is accomplished by treatment of the free acids of the cyclic nucleotides with the corresponding 7(dialkylamino)-substituted 4(diazomethyl)coumarins. Irradiation of the DMACM- and DEACM-caged cyclic nucleotides with UV light stimulates the release of the cyclic nucleotides within roughly a nanosecond. The new caged compounds are resistant to hydrolysis in aqueous buffers and exhibit long-wavelength absorption properties with maxima at 400 nm, high extinction coefficients, and high quantum yields (0.15-0.31). Their favorable properties render these compounds the most efficient and rapid phototriggers of 8-bromo-substituted cyclic nucleotides known. The usefulness of the compounds for physiological studies under nondamaging light conditions was examined in HEK293 cells expressing the alpha subunit of the cyclic-nucleotide-gated (CNG) channel of cone photoreceptors (CNGA3) and of olfactory neurons (CNGA2) by using confocal laser scanning microscopy and the patch clamp technique.     

DESENSITIZING EFFECT OF ISOMERIC METALLORGANIC PALLADIUM (II) COMPOUNDS WITH THIOSEMICA-RBAZIDE ON THE DEVELOPMENT PROCESS OF SILVER HALIDE PHOTOGRAPHIC MATERIALS

Some chemical compounds can be used in the chemical photographic development process of silver halide panchromatic motion picture materials to decrease their sensitivity upon exposure whereby their development is possible at relatively bright illumination. Such compounds can be the organic compounds of o-elements with complanar structure. It was observed, in particular, the pronounced desensitizing effect of bis (thiosemicarbazido) palladium (Ⅱ) dichloride of the formula:     

碳还原剂加入方式对粉煤灰氮化反应的影响

通过碳还原氮化反应,从工业废料粉煤灰制备氮化陶瓷类材料.采用氮/氧分析仪测定产物氮含量,评价氮化反应程度;以BET氮气吸附法测定比表面积,分析粉体活性;以扫描电镜分析样品表面形貌;以热重分析仪测定碳含量,X射线能谱仪估计元素组成.比较机械混合法、超声法和高能球磨法3种碳加入方式.结果表明,粉煤灰自身含碳的还原活性处于机械混合法和高能球磨混合法之间,高能球磨法对提高反应混合物活性最有效,所得产物结晶氮含量最高,质量分数可由0.3 %提高到23.1%.     

Effect of vanadium and chromium on the microstructural features of V–Cr–Mn–Ni spheroidal carbide cast irons

The objective of this investigation is to study the influence of vanadium（5.0wt%–10.0wt%） and chromium（0–9.0wt%） on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys＇ microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic（based on M7C3）, pearlite, martensite, and austenite. Their combinations and area fraction（AF） ratios are reported to be influenced by the alloys＇ chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic（γ-Fe ＋ М7С3）, preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.     

Evaluation of Process Capability in Gas Carburizing Process to Achieve Quality through Limit Design Concept

NUMEROUS INDUSTRIAL APPLICATIONS requirea hard wear-resistant surface called the case,and arelatively soft,tough inside called the core.There arefive principal methods of case hardening:?Carburizing?Nitriding?Cyaniding or carbonitriding?Flame hardening?Induction hardeningThe first three methods change the chemicalcomposition,carburizing by the addition of carbon,nitriding by the addition of nitrogen and cyaniding bythe addition of both carbon and nitrogen.The last twomethods do n…     

Computer Simulation of the Process of Quenching Large-Size Parts in Water and Aqueous Solutions

DESPITE of the rapid development of computerfacilities and numerical methods of computing thestress-strain state of large-size parts,the accuracy ofcomputations is not sufficient because of the lack ofaccurate input data.For this reason,heat treatingengineers do not trust computations and are afraid ofquenching of large-size parts in water,in particular,when Bi—>°°.There are some causes of suchsituation:1)Because of inaccurate boundary conditions andincomplete information on mechanical p…     

多孔材料:现状和发展趋向

本文评论了近半个世纪以来有关多孔材料的现状和发展趋向。指出了利用多孔材料的孔隙度、孔径分布、渗透性及缓冲能力、毛细管引力、电阻、耐磨性、高的比表面及表面张力等性质,而在可渗透材料、轴承、蓄电池、燃料/空气电池、医学领域、密封圈、灯芯、发散冷却、振动缓冲、模的润滑、原子能工业等方面的应用。较为详细地叙述了多孔材料在过滤、轴承、碱性蓄电池电极板三方面的应用。同时也指出了多孔材料     

A302B类钢室温疲劳试样的断口组织照片和显微组织分析

<正> 本文通过对A302B类铁素体压力容器钢室温试验的试样显微镜分析,描述材料的断裂过程并确定它与疲劳裂纹扩展数据的关系。断裂试样用了扫描电镜(SEM)、电子照相技术和能散X射线显微分析作检查。对切自T-L方向的试样的断面所作的扫描电镜检查披露了存在着在所观察倒的ΔK临界值以上时夹杂物带。随后所进行的X射线影象扫描以及目对应的能谱表明带区是硫化锰夹杂。这些试样在夹杂物带区上的裂纹扩展速度与L-T向试样相仿。产生夹